PARIS — It was 10:45 on a gray, chilly January morning here. The conductor Philippe Jordan was spending a rehearsal break on a couch in his spacious office at the Bastille Opera House, looking through the score of Mozart’s “Così Fan Tutte.” He had already spent an hour with the Paris Opera’s orchestra going over “Così,” which was two weeks away from opening in a new production directed by the Belgian choreographer Anne Teresa de Keersmaeker.

“There is such a thin line between perfection and energy and life in Mozart,” Mr. Jordan said as he walked back to the rehearsal. “It takes a lot of work.”

Every day is a lot of work for Mr. Jordan, who was appointed the Paris Opera’s music director in 2007, when he was just 33, and has swiftly risen to become one of the most sought-after conductors of his generation. At any moment, he is juggling preparations for several opera productions and orchestral concerts here (he will conduct 49 performances at the Paris Opera this season), as well as engagements abroad. In August, he will conduct a new staging of Wagner’s “Die Meistersinger von Nürnberg” at the Bayreuth Festival in Germany, and he will return to the Metropolitan Opera in the spring of 2019 for a crucial assignment: a full revival of Robert Lepage’s controversial production of Wagner’s “Ring” cycle.

“I’ve seen the DVD,” he said when asked about the production and its huge, wonky seesaw set. “Even Peter Gelb is clear that things have to be changed, and I’ve made a list and given some suggestions. Revivals give you the chance to make things better.”

This January, however, he was in Paris, working on both “Così” and Wagner’s “Lohengrin,” the only one of that composer’s operas he hadn’t yet conducted. In the corridor of the Bastille, he crossed paths with the tenor Jonas Kaufmann, who was scheduled to sing Lohengrin after a much-publicized monthslong pause to recover from a burst blood vessel on his vocal cords. “Don’t come near me, I have a cold!” Mr. Jordan said, and Mr. Kaufmann scooted back dramatically, with a laugh.

“The quality of the casts that Paris is getting now is really quite frightening,” Mr. Kaufmann said in an interview the next day. “I think that one of the ingredients is Philippe, because you are guaranteed a superb musical quality and a conductor who has not made up his mind about how you should sing a role. We always find a solution and an inspiring interpretation.”
11 a.m.

The break over, Mr. Jordan resumed work with the orchestra. Or, rather, one of them. The Paris Opera has a large enough ensemble to be able to have two orchestras — coded green and blue — rehearsing and performing simultaneously. (Mr. Jordan was working with Team Blue.) As the musicians began Act I of “Così,” he exhorted different sections to emphasize specific tonal qualities, using a torrent of onomatopoeic sounds. “Tssshhhtt!” he hissed during a quiet section; “Yip-yip!” as the tempo quickened.

During a recitative passage, Mr. Jordan sang the singers’ parts in Italian, calling out instructions between the lines. “When you argue with singers about color or the right tempi,” he said later, “you need to feel the rubato of the language. I learn every line and if I can’t pronounce the words, I feel like my hands are tied. Perhaps in 10 years I’ll learn Russian and do all the Russian operas.”
12:30 p.m.

Over lunch at a nearby restaurant, Mr. Jordan spoke about his childhood in Zurich and his musical training. Born to the noted Swiss conductor Armin Jordan, who died in 2006, Philippe knew he wanted to follow in his father’s footsteps by the time he was 9. “I never had the astronaut or fireman phase,” he said.

At 15, he left ordinary school for the Zurich Conservatory, and completed a piano diploma — “in case the conducting thing didn’t work,” he said — as well as studying composition. By 18, he was assisting Jeffrey Tate on a “Ring” cycle at the Théâtre du Châtelet, headed at the time by Stéphane Lissner. Now the director of the Paris Opera, Mr. Lissner said that Mr. Jordan stood out immediately. “His rigorousness, the quality of his preparation, his theatrical sense, were evident even then,” Mr. Lissner said in an interview.

At 20, Mr. Jordan was hired as the concertmaster of the Ulm Stadttheater in Germany. “I learned conducting the old-fashioned way, like Karajan, Kleiber, Mahler,” he said. “You play the piano through rehearsals, you step in to conduct for half an hour, you conduct operetta, which is hard. Today this is out of fashion: You do your studies, win a conductor’s competition and your career begins. But you have no idea about guiding the machine. It’s not fun to hear, but sit on a piano in a German opera house for four or five years and learn your job.”

He said it was important for his personal growth to get away to Ulm, and later to Berlin, where he worked as Daniel Barenboim’s assistant for three years at the Staatsoper. “My father was a big personality and I was immersed in his world, which was a blessing and a curse,” Mr. Jordan said. “Later, I could go back to him and realize: That’s part of me and I can be proud of it.”
2:30 p.m.

Back in a Bastille rehearsal studio, with a panoramic view of Paris rooftops, Mr. Jordan was taking six singers through the recitative passages of “Così,” which he described as particularly vital in Ms. De Keersmaeker’s production, which uses both a singer and a dancer to interpret each principal role.

“Because you have little action, and the dancers are moving, we have to do everything with rhythm and tempo,” he told the singers. “Really make it strong.”

Speaking alternately in English, German and Italian to the international cast, he urged them to greater clarity of expression, diction and meaning, often discussing the potential intention of a phrase. “More bite, more hate!” he called out to Simone Del Savio, playing the chilly Don Alfonso. “Ah, that’s so cynical and nasty — lovely!”
6:30 p.m.

At a traditional internal presentation of New Year’s wishes, Mr. Lissner gave a short speech to about 70 orchestra and technical staff members in an upper foyer of the opera house. After listing some triumphs and challenges of the past year, he gestured to Mr. Jordan and said: “Not many musical directors are as engaged with both the performances and the daily life of the house as Philippe.” Mr. Jordan, whose slight cold had worsened, spoke briefly in a hoarse voice, highlighting the orchestra’s achievement in playing Bach at a recent concert.

He added in a conversation that part of his job at the opera, where he is in charge of about 300 people, involves successfully interacting with a variety of personalities. He said he learned much about this in his first job as a principal conductor, in Graz, Austria, where he went after leaving his post with Mr. Barenboim in Berlin.

“I was now really my own boss, at 27,” he said, “and I had to learn that the psychology of working with people is not always easy.”

After three years in Graz, he freelanced, making debuts at the Glyndebourne Festival in England, the Aix-en-Provence Festival in France, the Royal Opera House in London and the Metropolitan Opera. While it was an active period, when Nicolas Joel, then the director of the Paris Opera, offered Mr. Jordan the music directorship, he decided it was time to commit.

“Internationally, the Paris Opera didn’t have a great reputation compared to, say, the Met,” Mr. Jordan said. “But my father used to tell me it was good, and I felt that after the one-night stands of being a freelancer, it was time to have a serious relationship, a marriage with an ensemble which you work with on a daily basis.”

In 2014 he added another post, becoming the chief conductor of the Vienna Symphony Orchestra. “If you are only an orchestra conductor, or only an opera conductor,” he said, “you’re only doing half the job.”
7:30 p.m.

After a day of “Così,” an evening stage rehearsal of “Lohengrin” began, with Mr. Jordan, now almost voiceless, leading the orchestra and singers through the first act. A chorus member twisted her ankle, and the rehearsal was suspended for 10 minutes. Sounding stressed for the first time in a busy day, he announced through a microphone: “We need to move on if we’re going to get through everything.”

Mr. Jordan’s current contract in Paris runs through 2021; he said he is likely to leave then, when Mr. Lissner, 64, plans to retire. “I have loved the intellectual approach that Stefan has brought to the Opera,” Mr. Jordan said. “He is clever because he also knows how to enchant Paris audiences. It can be very modern, but must always look very good.”

At 10:30, the rehearsal ended. The orchestra applauded Mr. Jordan, who smiled. “See you tomorrow,” he said.